Manufacture of laminated films



Feb. 16, 1937. D, w, HANSEN 2,070,59

"MANUFACTURE OF LAMINATED FILMS- Filed Dec. 11, 1935 "4 1 [As/LY STQ/PPA BLE HLM As Of Caz UL 055 [5 75/? [3/455 BASE C/asr o/v CELL (/1. 05E [5?"- n/ SECOND Hm AS OF P/POLAM/NE i5 5/? f7LM,/l/JH/2E/vr 7745/95 7'0,A/VD G 0 UNITED To 1r AFTER \57'/?/PP/NG LAss E METAL h A v I r SURFACE I fAs/LY STIQIP/JABLE J1 g 10 F/LM As 0F CELLULOSE 5 TEE BASE 11 j F/uv B F/LM A 10 Ewe 72.204

Patented Feb. 16, 1937 2,070,596 MANUFACTURE OF. LAMINATED FILMS Donald W. Hansen, Decatur,

, mesne assignments,

Ill., assignor, by to Prolamine Products Incorporated, Dover, Del., a corporation of Delaware Application December 11, 1933, Serial No. 70l,865fl '1 Claims.

The present'invention relates to the manufacture of films and has particular reference to the casting of films on smooth surfaces. I

Itls a custom in making films to flow a liquid or viscous mixture onto a smooth surface where the mass sets, as for example by the evaporation of a solvent. Sometimes glass is used, other times polished metal, and sometimes mercury. The latter is particularly necessary where the dried or set film is adherent to solid surfaces such as glass or metal. The selection of the solid surface material is in part predetermined by thefilm composition to.

tendency of a particular adhere in the forming process.

Films so formed are thereafter frequently coated with a surfacing composition to give to the ultimate sheet certain properties which are not exhibited by the body of the film. As an example of such coating, reference is made to the practice of applying a waterproofing nitrocellulose lacquer to a regenerated cellulose to form what is commercially recognized as waterproof cellophane.

The present invention relates to the formation of such a multiplex film, and has particular utility in casting films which have a tendency to adhere to a casting surface, or in other words which do not readily strip from a casting surface. The invention calls for the formation of a film which does strip readily face onto which another film may be cast.

The general object of the invention is the formation of a strippable film on a casting surface, and the casting on said film of a second film,

35 and stripping the two films together from the casting surface.- i

A particular object of the invention is the casting of a film-forming composition, which normally adheres to a casting surface, upon a preformed unstripped cast film strippable from its casting surface.

A further object of the invention is the formation of a casting surface for films in the form of a strippable unstripped film.

Still another object of the inventionis the casting of a prolamine base film onto a strippable unstrippedfilm of cellulose ester base.

A further object of the invention is the formation of a duplex film of which one layer is a prolamine base film. v I

Still another object of ,the invention is the formation of a triplex film of which the inner layer is a prolamine base film. 7

Various other and ancillary objects and advantages of the invention will be apparent from from a casting surface, 30 thus to provide by such film a new'casting surwhich is readily the following description and explanation of the invention. V 7

In the accompanyingdrawing there is showndiagrammatically a representation of the inven-' tion and the process.

Fig. 1 represents a casting surface of cellulose ester film itself cast on and remaining unstripped from a solid smoothsurfaced body. s

Fig. 2 represents the cast of Fig. 1 after a second film has been cast thereon, and also shows the united films being stripped from the solid body. h

Fig. 3 represents the form of Fig. '2 with a third film applied before the stripping operation.v

In carrying out the invention a smooth surfaced bodyof glass,.po lished metal or stone may be employed as asolid cast. This may be fiat as a plate for making sheets or curved as a cylinder for forming continuous sheets, or some suitable form from which a non-adherent film cast 20 thereon'may be stripped without destroying the continuity of the film. In the drawing a fiat form l0 is illustrated. Onto the cast) I form a film of any suitable material, necessarily char acterized by ability to strip readily from the cast l0. A very'thin or thick film may be formed, and it may be formed by setting of a mass, or by the evaporation of a solvent from a solution applied to the surface ll of cast lit. The filmis designated i2 and its surface is designated IS. The coated cast I0 thus forms a new cast forthe second film and a new casting surface l3.

Onto the new casting surface I3 I form a second film [4 characterized by ability to adhere to the film l2. The new film H may be set from a mass applied, or may be formed by applying a solution to thesurface l3- and evaporating solventfrom the solution. In the latter event, the solvent may be such as to soften or partially dissolve the material of film l2, but this is not necessary if adherence is otherwise obtained or naturally results I from the nature of the materials. I

When the new or second'film I4 is dried the two films, whichare now united, may be stripped as one film from the solid cast Hi. The product is a duplex film with layers of differentamaterials'on the two-sides. I I I If desired a third layer l5 may be applied to layr l4 before thestripping operation as shown in Fig. 3. The third layer may bethe sameor different from the first layer l2. It is :preferred to make it the same as the first filmso that the resulting triplex product may have a heavy middle layer as a body, and similar thin coating layers for special surface properties. In

v the drawing the three layers are designated film metal, etc.

vent,'the concentration, the presence 'of'plasti 35 Alcohol soluble cellulose nitrate 'Ethyleneglycol monoethyl ether. 1,0

Ethyl alcohol 90 4.0 a Cellulose acetate -11 p In actually carrying out the invention I have applied it by using as film B a prolarnine base film, asof zein, hordein or gliadin. Such films ,may be formed from aqueous alcoholic solution and have atendency .to adhere to glass, polished .1

I- havefound, howeverpthatthe tendency o'fprolamine solutions, to adhere in filmformation, is dependent upon manyfactors, and

is not easily'predictable. The character of 501- 1 cize'rs, the presence of anti-blushing'agents and of other modifying agents, the characterof the casting surface, the temperature of drying, tc.-,

are all factors affecting this property of herence or 'ofstripplng a formed film. I, I have also found that film-forming prolarnine base solutions which do and which do not strip easilyhave thepower of adhering to othercast films, particularly to cellulose ester base films. Thisis more particularlytruewhen the cellulose ester base film contains material, preferably the cellulose ester base itself, which-is softened by "or which is soluble in solvent material used in the film-forming prolaminesolutioni.

In'practice, therefore, Iiuse a cellulose ester base film as a casting surface for a prolamine base film I prefer a cellulose ester film which gives valuable surface properties to the resulting product.

. \The following formulasare suitable for film A5 I Formula No.-1f

Parts by weight 1 r forma laNoJ I Parts by wei t Ethyl lactate j Acetone .L 90

These solutions may be applied onto glass,

polished metal and the like, and will dry in about 5 minutes at 125 F. The examples show quick dryingsolvents such as alcohol and acetone, and

' also slowly volatile high-boiling solvents.'Upon lossof the highly volatile solventabout, 10.% of the-original solution remains as adry solid. It is set and non-tacky but is not a strong-tenuous film. inasmuch as it has only about ester'in its make-up. The'rest is plasticizing solvent whichcan be lost by seasoning or" further exposure. Presence of some of this higher boiling solvent assures strippability 'of the film, but not until it is reinforced by the film to be cast upon it. .It-does not matter what composition the film has, because, the essential requirement isiits strippability. The solution is preferably applied to' form afilm about 0,00905t9 0.0001

4' inch in thickness. Ifit is too thin,;.it mayldissolve' inthe solvents of the applied,p'rolaminecomposition. Itisto be understood thatthethickness ofr-the film above specified is given .only by way of'example, and is not to be considered as any essential limitation. Formula No. 1, is preferred for the-prolarnine compositions hereinafter given because bothhavethe samesolvents and one recovery system may be employed; Proofing agents may beadded to the formulas, as by following the general disclosures of the Charch and Prlndle U; S. Patents Nos. 1,826,697 to"1,826,699. Where formulas like those" of Charch and Prindle are...

hereby incorporated by used for proofing compositions to be applied to prolamine films already formed and stripped, it is advisable to omit ethyl alcohol or other-alcohol, which is a quick solvent for zein, or it will cause the zein film tostretch and curl, Thus, where'film C isto be applied to film B, itis preferred to'apply the composition for film C beforethe stripping operation. In suchcase the "precaution as to the alcohol need not be so fully, observed.

Prolamine film.For the prolarnine film I may use zein, hordein or .gliadin bases. Using zein,

the following composition is suitable. To '75 parts by weight of 12% zein solution in a solvent consisting: of f 70%' of ethyl alcohol and 30%v of water, or to any equivalent solution/I may add a leveling solvent, preferably lo parts'by weight, suchas ethylene glycol monoethyl ethen' As aplasticizer'I may add 2 parts by weight of dibutyltartrate. 'As an anti-blushing agent, I

may add on the basisof zein 2% .to 3%,of material such as monoethanolamine salt or monopro panolamine salt, such as an acetate or lactate salt. In addition there is added aprotein fixative suchas 2.5 parts by weight of 37% formaldehyde solution, or-a small quantity of glyoxal. f'I'his'- composition may be spread to dry onto the film A. to form film B.. E .f j

In the above description it is to be understood that many variations of the zein solution are per-v mitted, and some of these arefgiven in full in my copending application Serial No. 701,863, filed December 11, 1933; All the disclosures for prolamine base compositions.thereinfgiven are reference in this application.- V p In the example above given the-use of fixing agent such as formaldehyde aids in producing a strippable film, yet its use is not to. assure strippabi1ity.. When fixing agentfis not usedit is usually impossible to strip a film from the casting in water or in alcohol, but only in aqueous alcohol,

it is necessary to guard the solvent for prolarnine from dilution to such extent that it becomes a n0n-solvent.- Thus, the'strippable film is first dried to assure that residual solvent content therein does not alter the prolamine solvent and precipitate prolarnine at theinterface. Another advantage of dryness for the strippable-film lies in the fact that the dry filmis more slowly affected or penetrated by solvent of the prolarnine,

compared to a still-wet strippable film.

I'claim':

a 1. The method of forming .aprolaminebase film with a. surface coat thereon which comprises forming a dry solid strippable film of cellulose ester base on a solid casting body with a surface, ifrom which the said film may be readily stripped,

casting a prolarnine base film'onto said firstformed film in adhesive union thereto,'and stripping the united films asa single body from the solid casting body.

2. The method of forming a prolamlne base film with a surface coat thereon which comprises forming a dry solid strippable film of cellulose ester base on a solid casting body with a surface from which the said film may be readily stripped, casting a prolamine base film onto said firstformed film in adhesive union thereto, forming a third film of cellulose ester base on said prolamine base film in adhesive union thereto, and stripping the united films as a single body from the solid casting body.

3. The method of forming a prolamine base film with a surface coat thereon which comprises forming on a surface of a solid casting body a dry solid strippable film of cellulose ester base which is softened by or soluble in an alcohol solvent, the casting surface of said body being such as to permit stripping said film without destroying the continuity thereof, casting onto said film a film-forming solution of prolamine base and alcohol solvent which is a softener or solvent for said cellulose ester base, drying out the solvent whereby to form a prolamine base film in adhesive union with the cellulose ester base film, and stripping the united film as one'body from the solid casting body.

4. The method of forming a prolamine base film with a surface coat thereon which comprises forming on a surface of a solid casting body a dry solid strippable film of cellulose ester base which is softened by or soluble in an alcohol solvent, the casting surface of said body being such as to permit stripping said film without destroying the continuity thereof, casting onto said film a film-forming solution of prolamine base and alcohol solvent which is a softener or solvent for said cellulose ester base, drying out the solvent whereby to form a prolamine base film in adhesive union with the cellulose ester base film, forming a third film by casting on the prolamine base film a cellulose ester base composition containing prolamine solvent, evaporating the solvent from the third film, and stripping the united film as one body from the solid casting body.

5. The method of forming a zein base film with a surface coat thereon which comprises forming a dry solid strippable film of alcohol-soluble nitrocellulose base on a solid casting body with a surface from which the said film may be readily stripped, coating an alcoholic solution of zein base film-forming composition onto said nitrocellulose film, drying out the volatile solvent of said zein composition, and stripping the resulting united films together as one body from the solid o casting body.

6. The method of forming a zeinbase film with a surface coat thereon which comprises forming a dry solid strippable film of alcohol-soluble nitro cellulose base on a solid casting body with a surface from which the said film may be readily stripped, coating an alcoholic solution of zein base fihn-forming composition onto said nitrocellulose film, drying out the volatile solvent of said zein composition, casting on the zein film a third film of base composition different from the mg a solution of zein base film-forming composition onto said cellulose acetate film, drying out the volatile solvent of said zein composition, and stripping the resulting united films together as one body from the solid casting body.

a DONALD W. HANSEN. 

